Stochastic effects of charge transfer on image interaction and plasmon excitation in ion-surface grazing scattering

We model the charge-state evolution of fast hydrogen-like ions in the course of grazing scattering from metal surfaces by a Markov process with the time-dependent jump coefficients. Using the master equation for charge exchange, we show that the process may be treated as quasi-stationary owing to the adiabatically slow ion motion in the direction perpendicular to the surface. We further employ the dielectric formalism within the specular reflection model and the plasmon-pole approximation to evaluate the expectation values for the ion-image interaction with the surface and the rate of surface-plasmon excitation. We find that, close to the surface, both these quantities are significantly affected by the projectile-charge fluctuations. In particular, we find a substantial rate of the plasmon excitation for ion velocities well below the threshold implied by the kinematic constraint. (c) 2005 Elsevier B.V. All rights reserved.